Pharmacoepidemiology is a bridge science that uses tools from pharmacology, epidemiology and clinical medicine to understand the use, safety and effectiveness of drugs in large populations. The need for experts in this field has never been greater. During the past decade, dozens of new therapies have been brought to market, including products made from living cells, or biologics, to address common and costly heart, lung and blood conditions ranging from homozygous familial hypercholesterolemia to idiopathic pulmonary fibrosis to Hemophilia A. With the rise in access to promising yet expensive drugs comes the need to study their benefits and risks in diverse populations as well as to understand best use of these medicines to improve human health. In addition, many of pharmacoepidemiology's tools and methods are also highly relevant to the study of use, safety and effectiveness of other medical products including diagnostics, devices, and drug-device combinations. We propose a training program in pharmacoepidemiology for pre- and post-doctoral trainees at the Johns Hopkins Bloomberg School of Public Health and Johns Hopkins School of Medicine. These institutions are exceptionally well suited to this task. The Bloomberg School of Public Health is the oldest and largest School of Public Health in the world, having celebrated its centennial this year, while the Johns Hopkins School of Medicine is an internationally renowned leader in scientific research and clinical medicine. Our proposed program will leverage a wealth of human capital and material resources at Johns Hopkins to provide comprehensive, longitudinal, and integrated training and professional development opportunities to future leaders in the field. We will use this award to train scientists who will identify and address fundamental questions about the use, safety and effectiveness of medicines and other medical products for the treatment of heart, lung and blood diseases. Given the strengths of our faculty and trainee pool, we will also support the development of innovative methods to do so. Thus, our trainees will develop skills to generate evidence that can be used to address the needs of patients, clinicians, payers, regulators and other stakeholders, and in so doing, improve the optimal use of medicines to treat heart, lung and blood diseases in the United States.